Cold-rolled coils leave the mill with a pickled, rolled and often oiled surface that is highly reactive. During transport, the enemy list is short but aggressive: humidity, condensation, salt, dust, and physical damage to edges. Wrapping film is the first line of defence, and the right choice of film depends on the route, the duration and the value of the material.
Why Wrapping Is Necessary
Moisture and rust prevention: stretch film forms a physical barrier that isolates the coil surface from humid air, especially important on coastal routes and sea freight, where salt-laden spray is common.
Active corrosion control: VCI (volatile corrosion inhibitor) film releases inhibitor molecules inside the wrap, which adsorb on the steel surface and suppress corrosion even where the film is locally damaged.
Dust and contamination control: road transport splashes mud, oil and dust onto the surface, which can ruin subsequent painting or welding and trigger customer complaints.
Mechanical security: the film, together with edge protectors and bore sleeves, holds the coil on its saddle and shields edges from friction against other cargo.
Packaging Levels Compared
| Level | Description | Best for |
|---|---|---|
| Stretch film wrap | Single or double layer of PE stretch film plus edge protectors | Domestic land transport, short storage, general rust prevention |
| VCI composite packaging | VCI film or VCI paper + desiccant + waterproof vapour barrier | Export sea freight, coastal transport, high-value coils, medium- and long-term warehousing |
| Simple packaging | Corner protectors and inner bore sleeve only, no full wrap | Short-distance movement of galvanized or coated coils, in-plant turnover, by customer agreement |
Sea Freight and Long-Term Storage
For ocean containers, a single layer of stretch film is not enough. Standard export practice combines VCI rust-preventive film, rust-preventive paper, desiccant bags and a thick waterproof vapour barrier, all strapped on a wooden or steel saddle. The container should also be vented or fitted with desiccants according to the shipping line's instructions, because condensation cycles during the voyage are the main cause of container rust.
When Wrapping Is Not Necessary
In-plant transfer to the next process: coils going directly from the rolling mill to an adjacent annealing, galvanizing or colour-coating line do not need packaging.
Coated products on short routes: galvanized (GI), aluminium-zinc (GL) and other coated coils have an inherent zinc or aluminium-zinc protection; for short distances, edge protectors and bore sleeves may be sufficient.
Customer-driven simplification: some downstream users who unwind immediately accept simple packaging to save cost and reduce waste.
Frequently Asked Questions
1. What is VCI film?
VCI stands for volatile corrosion inhibitor. The film releases inhibitor vapour that saturates the enclosed air space and forms a protective molecular layer on the steel, giving active protection even in humid conditions.
2. Is stretch film enough for export?
For most sea freight, no. Use VCI composite packaging with desiccant and a vapour barrier, and keep the coil elevated on a dry saddle so it never sits in water.
3. Can wrapped coils be stored outdoors?
Short-term outdoor storage is possible under cover with the wrap intact, but the protection period depends on the packaging level. Plan storage on a dry, ventilated area and respect the supplier's maximum storage period.
4. Do galvanized coils need the same packaging?
No. The zinc coating provides corrosion reserve, so galvanized coils typically need only dust protection and edge protection for short journeys; heavy VCI packaging is reserved for long voyages or premium surface requirements.
5. Who pays for packaging?
Packaging is normally included in the export price, but the level should be confirmed in the order so that both sides share the same expectation of arrival condition.
6. How should the coil be stored after unwrapping?
Keep it in a dry warehouse below 60% relative humidity, keep the oil film intact or re-oil exposed surfaces, and protect cut edges with rust-preventive oil or paint.